The invention is based on a fuel injection valve for internal combustion engines. In one such fuel injection valve, known from German Utility Model 92 06 268.7, a valve body of the injection valve is axially secured with a tightening nut to a holder body that is inserted into the housing of the engine to be supplied. The valve body, on its free end, has at least one injection port protruding into the engine combustion chamber; this injection port adjoins a fuel inflow conduit extending in the valve body and the holder body, and it can communicate with the valve body by means of a movable valve member inside the valve body. The fuel inflow conduit in the holder body is formed by an axial longitudinal bore that discharges into the end face of the holder body facing toward the valve body and by a radial transverse bore intersecting the longitudinal bore; the injection port of the transverse bore forms a lateral pressure connection, on the radial circumferential wall face of the holder body, for a fuel delivery line that leads away from a high-pressure fuel pump. A pressure neck located at the lateral pressure connection formed at the injection port of the transverse bore connects the external fuel delivery line with the holder body. This pressure neck is braced against the holder body in the axial direction and radially to the axis of the holder body via tightening screws, and the holder body has to absorb all of these chucking forces.
The known fuel injection valve has the disadvantage that because of the chucking forces of the pressure neck on the lateral pressure connection that have to be absorbed, very high static stresses occur in the region of the bore intersection of the vertical longitudinal bore and the horizontal transverse bore of the fuel conduit inside the holder body. Under these static loads, it is of major significance whether they cause compressive or tensile stresses in the holder body; in the known fuel injection valve, the force introduction axis forms only a line on the circumferential wall and thus generates very great tensile stresses in the region of the bore intersection; this lowers the allowable pressure threshold value in this region.
At very high operating loads on the fuel injection valve, especially at high fuel pressures of over 1800 bar, the high static stresses, which occur particularly in the form of tangential tensile stresses in the region of the aforementioned bore intersection, lead to permanent breaks in the region of the bore intersection and thus to failure of the applicable fuel injection valves, making them unsuitable to use in injection systems that employ very high fuel injection pressures.
The risk of component failure in the holder body is still further increased by an oscillatory stress, such as from a pulsating internal pressure in the fuel conduit in cooperation with the high internal fuel pressure inside the fuel conduit and the static prestressing in the holder body.
The fuel injection valve for internal combustion engines according to the invention has the advantage over the prior art that line pressure, as in the known holder body, can be avoided, and opposite the bore intersection of the fuel conduit in the holder body, two line contacts are formed, laterally offset from the bore intersection, on the radial circumferential wall face opposite the lateral pressure connection. This is advantageously effected by the provision of an indented protrusion in the circumferential wall of the holder body, on its radial cs region opposite the lateral pressure connection. In this way, within the deformation and tension region, a tightening torque is generated that counteracts widening of the bore. This tightening torque is formed of the resultant forces at the holder body, which counteract the chucking force of the pressure neck on the lateral pressure connection. In addition to the contrary force that counteracts the axial chucking force on one axis, a force component extending at right angles to the contrary force also occurs, so that the aforementioned tension moments that counteract widening of the fuel inflow conduit bore are generated. In this way, lesser deformation and thus reduced tensile stress can be achieved inside the valve body, so that the bracing of the pressure neck on the lateral pressure connection no longer increases the inherent stresses, and in particular the tensile stresses of the holder body, to an impermissible extent. This reduction of the inherent stresses in the holder body leads to greater strength and thus a longer service life of the holder body of the fuel injection valve of the invention, even at operating pressures of up to 2000 bar and under alternating oscillatory stress.
The indented protrusion opposite the lateral pressure connection on the holder body is preferably embodied as material erosion from the radial circumferential wall of the holder body, but it is alternatively possible to incorporate this feature into the original forming of the holder body. The material erosion of the indented protrusion on the holder body is preferably embodied as a plane ground section, and the transition edges formed between the plane ground section and the remaining radial circumferential wall region of the holder body are located outside a force introduction axis of the lateral pressure connection. With this shifting of the line of contact on the radial circumferential wall to two lateral lines of contact, the material comprising the holder body is positively displaced inward by the aforementioned tightening moment, and the result is that tensile stresses are reduced, or that compressive stresses now occur in the region of the bore intersection that counteract its widening. This is especially advantageously effective in high-strength materials with a high mean stress vulnerability (such as 42CRM04PB).
The lateral pressure connection on the holder body can, as shown for the exemplary embodiment, be disposed perpendicular to the axis of the holder body, but an inclined placement is also possible as an alternative. A plane ground section is also shown and described in the exemplary embodiment, but the indented protrusions on the circumference of the holder body can alternatively take other forms as well, such as crowned or convex surfaces.
With the fuel injection valve of the invention, it is thus possible to increase the resistance of the holder body to oscillatory stresses and static loads considerably, without increasing the space originally required for installing the fuel injection valve.